A series of end-capped oligomers 17, 21, 25 and 28 related to nylon 4 6, and 39, 43, 47 and 50 related to nylon 6 6 have been prepared starting from adipic acid monoethyl ester 6, the alpha,omega-di-secondary diamines 8 and 29 and their mono end-protected derivatives 7 and 30, respectively, using the reactions of polypeptide chemistry. The formation of N-protected secondary amide bonds bearing the N-p-methoxybenzyl group ensured the solubility of all intermediates in common organic solvents and enabled purification by chromatography; boiling trifluoroacetic acid removed the protecting group in the final stage of the synthesis.